Hand-held machine tool for grinding, polishing, or the like

ABSTRACT

The invention is based on a hand power tool for grinding, polishing, or the like, having a drive motor, a gear coupled with the drive motor, and a grinding wheel ( 28 ) operatively connected to the gear. 
     It is proposed that the gear has a switch device ( 30 ), by means of which at least two types of grinding wheel motion can be selectable.

PRIOR ART

The invention is based on a hand power tool for grinding, polishing, orthe like, as generically defined by the preamble to claim 1.

It is known for a hand power tool of the type defined above to bedesigned such that with it, both a grinding wheel motion of anoscillating grinder and a grinding wheel motion of an eccentric grindercan be achieved. The grinding wheel motion of an oscillating grinder ischaracterized by an orbital motion, which is also called eccentricmotion, while the grinding wheel motion of an eccentric grinder ischaracterized by an orbital motion and a rotary motion. A hand powertool that can be used as both an oscillating grinder and an eccentricgrinder is a so-called multipurpose grinder.

The choice of the particular grinding wheel type of motion in such handpower tools is made by attaching a suitably embodied grinding plate.

ADVANTAGES OF THE INVENTION

The invention is based on a hand power tool for grinding, polishing, orthe like, having a drive motor, a gear coupled with the drive motor, anda grinding wheel operatively connected to the gear.

It is proposed that the gear has a switch device, by means of which atleast two types of grinding wheel motion can be preselectable. A handpower tool embodied in this way has the advantage that the tool can beadapted, without assembly operations, to the particular type of motionof the grinding wheel required, without changing the grinding wheel.Thus the hand power tool of the invention offers great ease of use andgreat flexibility in terms of the conditions under which it is used.

In an advantageous embodiment of the hand power tool of the invention,in at least one selectable type of motion, an orbital motion of thegrinding wheel is effected. In that case, for at least one preselectableoperating mode, an oscillating grinder is available to the user.

In at least one preselectable type of motion, a self-rotation of thegrinding wheel can be effected. The rotation can be tripped either bythe orbital motion of the grinding wheel, or, if the grinding wheel isin a freewheeling mode with regard to a rotation, the rotation can betripped by the operation of machining a surface. With a freewheelingmode relative to rotation, an especially high quality of the surfacetreated by means of the power tool can be achieved, since because thegrinding wheel can optionally yield rotationally to resistance, thefreewheeling mode leads to gentle surface treatment.

If an orbital motion of the grinding wheel trips a self-rotation of thegrinding wheel, the grinding wheel is subjected to a so-called forceddrive. As a rule, this happens in such a way that via an armature shaftof the drive motor and an eccentric sleeve connected to the drive motor,an additional self-rotation is forced on the grinding wheel.

However, it is also conceivable for a purely rotary motion orexclusively a self-rotation of the grinding wheel, for example, to bepreselectable by means of the switch device.

It is also conceivable that by means of the switch device, variouseccentric strokes or various rotary speeds of the grinding wheel can bepreselected.

In a preferred embodiment of the hand power tool of the invention, theswitch device cooperates with two gear wheels that mesh with oneanother, of which one is connected to the grinding wheel.

The hand power tool of the invention can be designed such that arotation of at least one of the gear wheels can be prevented by means ofthe switch device. Thus the rotational behavior of the two gear wheelsand the relative motion of them to one another can advantageously bevaried, and the type of motion of the grinding wheel can thus be set.

A structurally particularly simple, space-saving embodiment of the handpower tool of the invention is obtained if the first gear wheelconnected to the grinding wheel has a set of external teeth, whichmeshes with a set of internal teeth of the other gear wheel. In thatcase, the first gear wheel is embodied as a so-called planet wheel, andthe second gear wheel is embodied as a so-called ring gear. By asuitable selection of gear wheels, a gear ratio can be set thatadvantageously allows a high oscillating frequency of the grindingwheel, at a simultaneously low rotary speed of the grinding wheel.

Expediently, the gear wheel having the internal teeth is disposed in aslide bearing ring. On the one hand, this gear wheel is thus supportedin a space-saving way, and on the other, there is the advantage thatupon rotation of this gear wheel, only slight frictional forces have tobe overcome. However, it is also conceivable for instance for the gearwheel with the inner teeth to be disposed in a roller bearing.

A structurally especially simple embodiment of the hand power tool ofthe invention is obtained if the switch device includes at least onelocking bolt, which cooperates with at least one recess in the firstgear wheel or in the second gear wheel. By means of such a locking bolt,it is simple to prevent a self-rotation of the respective gear wheel. Inthe case of a gear wheel with external teeth, embodied as a planetwheel, which is in contact on the one hand with the drive shaft of thedrive motor and on the other with the grinding wheel, is eccentricallysupported, and meshes with the inner teeth of a ring gear, theengagement of the locking bolt with the recess of the planet wheel,which recess, to compensate for the eccentric driving motion expedientlyhas a larger diameter than the locking bolt, causes an oscillatinggrinding motion, or a purely orbital motion of the grinding wheel, withthe ring gear in the slide bearing ring being carried along in slidingfashion.

However, if the locking bolt engages a recess of the ring gear, thuspreventing the rotation of the ring gear in the slide bearing ring, thena self-rotation is imposed on the planet wheel upon its eccentricmotion. Hence a self-rotation of the planet wheel is superimposed on theeccentric motion of the same planet wheel.

If the locking bolt engages neither a recess of the planet wheel nor arecess of the ring gear, then the planet wheel is in the freewheelingmode. The grinding wheel connected to the planet wheel can thus alsorotate freely.

Preferably, the switch device includes two locking bolts, namely a firstlocking bolt for engaging a recess of the first gear wheel and a secondlocking bolt for engaging a recess of the second gear wheel.

Advantageously, for shifting the at least one locking bolt, the switchdevice has a switching ring. The switching ring acts as the actuatingdevice for the at least one locking bolt. The switching ring issupported for instance in a preferably two-part housing of the gear andis actuatable in the circumferential direction.

Preferably, the switching ring has at least one axial, circular-arclikerecess, in which a locking bolt is guided. If the switch device has twolocking bolts, then the switching ring preferably has two recesses, withone locking bolt guided in each recess.

Advantageously, the switching ring, in the region of the axial,circular-arclike recess, has a ramplike chamfer, by means of which theat least one locking bolt is axially shiftable by rotation of theswitching ring. By suitable disposition of the chamfers, it is possiblefor one locking bolt, resting with a region of increased diameter on thetop side of the switching ring, to engage a recess of the first gearwheel in one position of the switching ring, and for the other lockingbolt, in a different position of the switching ring, to engage a recessof the second gear wheel.

In order to keep the at least one locking bolt in position, the lockingbolt is urged in the axial direction by means of a spring.

An especially simple embodiment of such a spring pertains in the case ofa sheet-metal spring, which engages a recess or slot in the locking boltand axially loads the locking bolt.

The switching ring can be manually actuated, so that it can be put intowhichever switching position is desired by simple manual shifting, or itcan be actuated by a control and/or regulating unit via an actuator.

To allow convenient use of the hand power tool of the invention on manysurfaces of different outlines without changing the grinding wheel, thegrinding wheel preferably has an outline which has at least one straightboundary edge and at least one curved boundary edge.

DRAWING

Further advantages will become apparent from the ensuing description ofthe drawing. In the drawing, one exemplary embodiment of the inventionis shown. The drawing, description and claims include numerouscharacteristics in combination. One skilled in the art will expedientlyconsider the characteristics individually as well and put them togetherto make useful further combinations.

Shown are:

FIG. 1, a schematically shown power grinder of the invention in theeccentric grinding mode, in fragmentary section;

FIG. 2, the power grinder of FIG. 1 in the oscillating grinding modewith a freewheeling mode, in a view corresponding to FIG. 1;

FIG. 3, the power grinder of FIG. 1 in the oscillating grinding mode, ina view corresponding to FIG. 1;

FIG. 4, a perspective view of a switch device of the power grinder ofFIG. 1;

FIG. 5, a schematic exploded view of the switch device of FIG. 1, withtwo meshing gear wheels; and

FIG. 6, a manual actuating device of the switch device shown in FIGS. 4and 5, in a side view.

In FIGS. 1-3, a hand power tool 10 is shown. The hand power tool 10includes an electric motor, not visible here, which is disposed in atool housing 12 and drives an armature shaft 14. The armature shaft, ina manner fixed against relative rotation, engages an eccentricallydisposed recess 16 of a so-called eccentric sleeve 18.

On the side shown at the bottom in FIGS. 1-3, the eccentric sleeve 18has a centrally disposed bore 20, which is engaged by a screw 22 thatserves to secure a first gear wheel 24. The first gear wheel 24 issecured rotatably on the eccentric sleeve 18 via a ball bearing 26 andis connected to a grinding wheel 28 in a manner fixed against relativerotation.

Depending on the intended application, the grinding wheel 28 can takevarious forms. FIGS. 1 and 2 each show a grinding wheel for theeccentric grinding mode. Conversely, FIG. 3 shows a grinding wheel 28for the oscillating grinding mode. However, for all preselectableoperating modes, a correspondingly suitable grinding wheel can be used.

Because of the shifted disposition of the recess 16 and the bore 20 ofthe eccentric sleeve 18, the grinding wheel 28 is supportedeccentrically relative to the armature shaft 14. During operation, theaxis of the grinding wheel 28 therefore always executes an eccentricmotion, that is, a so-called orbital motion, about the axis of thearmature shaft.

The power grinder 10 has a switch device 30, by means of which varioustypes of motion of the grinding wheel 28 can be preselected, and whichis shown in enlarged views in FIGS. 4-6. The switch device 30 has atwo-part housing 32, which is in contact with the tool housing 12 orforms a structural unit with it and which encloses, among otherelements, the first gear wheel 24. A slide bearing ring 36 is alsoreceived in an annular groove 34 of the housing 32; it serves a bearingfor a second gear wheel 38, with a set of internal teeth, not shown inthe drawing, that is disposed concentrically to the slide bearing ring36. The second gear wheel 38, thus embodied as a so-called ring gear,meshes with the first gear wheel 24, which has a set of external teeth,also not shown in the drawing, and acts as a so-called planet wheel. Themeshing region of the two gear wheels 24 and 38 shown in the drawing isidentified in each case by reference numeral 40.

The second gear wheel 38 is also provided with axial bores 42, disposedat regular intervals in the circumferential direction and embodiment inthe manner of blind bores (FIGS. 4-5). The gear wheel 24 with theexternal teeth is also provided with axial bores 44 disposed at regularintervals in the circumferential direction. However, they are embodiedas through bores.

The switch device 30 has a so-called switching ring 46, which is guideddisplaceably in the circumferential direction in the housing 32. Theswitching ring 46 has an actuating grip 48, which extends through aradial slot 50 in the housing 32 and is disposed displaceably in theradial slot 50 in the circumferential direction of the housing 32.

The switching ring 46 is disposed eccentrically relative to the housing32 and serves to preselect various types of motion of the grinding wheel28. To that end, the switching ring 46 has two curved recesses 52 and 54that extend axially through the switching ring 46. In the region of therecesses 52 and 54, two ramplike chamfers 56 and 58 are embodied on thetop side of the switching ring and connect an upper switching plane 60with a lower switching plane 62. In each of the recesses 52 and 54, arespective axially extending locking bolt 64 and 66 is guided. Thelocking bolt 64, which is somewhat longer than the locking bolt 66,serves to engage one of the bores 42 of the second gear wheel 38.Conversely, the locking bolt 66 serves to engage one of the bores 44 ofthe first gear wheel 24.

Each of the locking bolts 64 and 66 has a respective head 76 and 78,which on the top side of the switching ring 46, and in particular as afunction of the position of the switching ring 46, rests on either theupper switching plane 60 or the lower switching plane 62.

The locking bolts 64 and 66 are each urged in the axial direction, inthe direction of an engagement position with the bores 42 and 44,respectively, by a respective spring 68 and 70 embodied as a sheet-metalspring. The springs 68 and 70 engage slots 72, 74 on the heads 76, 78 ofthe bolts 64, 66 and are fastened in the housing 32 by their ends remotefrom the locking bolts.

In the switching position shown in FIG. 1, the switching ring 46 is in arotational position, in which the head 76 of the locking bolt 64 restson the lower switching plane 62, and thus the locking bolt 64 is in alowered position and with its lower end engages one of the blindborelike bores 42 in the second gear wheel 38. This secures the secondgear wheel 38 against relative rotation. Conversely, the head 78 of thelocking bolt 66 rests on the upper switching plane 60 of the switchingring 46, so that the first gear wheel 24 can rotate. In this switchingposition, the grinding wheel 28 is subjected during operation of thepower grinder 10 to an eccentric motion, as well as a self-rotation,because of a force drive exerted on the first gear wheel 24 by means ofthe second gear wheel 38.

In the switching position shown in FIG. 2, the switching ring 46 is in arotational position in which both the head 76 of the locking bolt 64 andthe head 78 of the locking bolt 66 rest on the upper switching plane 60.Thus neither the second gear wheel 38 nor the first gear wheel 24 issecured against relative rotation, and hence with respect to itsself-rotation, the first gear wheel 24 is in a freewheeling mode. Inthis switching position, the grinding wheel 28 is subjected duringoperation of the power grinder 10 to an eccentric motion, where thegrinding wheel 28 can rotate freely about its axis of rotation.

In the switching position shown in FIG. 3, the head 76 of the lockingbolt 64 rests on the upper switching plane 60, and the head 78 of thelocking bolt 66 rests on the lower switching plane 62 of the switchingring 46. Thus the locking bolt 66 engages a bore 44 of the first gearwheel 24, thereby securing the latter against relative rotation. Thediameter of the locking bolt 66 is less than that of the bores 44, sothat in operation of the power grinder, the eccentric motions of thefirst gear wheel 24 about the armature shaft 14 can be compensated for.In this switching position, in operation of the power grinder 10, thegrinding wheel 28 is subjected to an oscillating grinding motion, or inother words a purely eccentric motion.

List of Reference Numerals

10 Power grinder

12 Tool housing

14 Armature shaft

16 Recess

18 Eccentric sleeve

20 Bore

22 Screw

24 Gear wheel

26 Ball bearing

28 Grinding wheel

30 Switch device

32 Housing

34 Annular groove

36 Slide bearing ring

38 Gear wheel

40 Meshing region

42 Bores

44 Bores

46 switching ring

48 Grip

50 Slot

52 Recess

54 Recess

56 Chamfer

58 Chamfer

60 Upper switching plane

62 Lower switching plane

64 Locking bolt

66 Locking bolt

68 Spring

70 Spring

72 Slot

74 Slot

76 Head

78 Head

What is claimed is:
 1. A hand power tool for grinding or polishing,comprising a drive motor, a gear coupled with the drive motor, and agrinding wheel (28) operatively connected to the gear, wherein the gearhas a switch device (30), wherein at least two types of grinding wheelmotion can be preselectable by means of the switch device, wherein theswitch device cooperates with two gear wheels that mesh with oneanother, wherein one of said gear wheels is connected to the grindingwheel, wherein the switch device includes at least one locking bolt,wherein said locking bolt cooperates with at least one recess in a firstone of the two gear wheels or a second one of the two gear wheels,wherein the switch device has a switching ring, wherein the at least onelocking bolt is switchable by means of said switching ring.
 2. The handpower tool of claim 1, wherein in at least one preselectable type ofmotion, an orbital motion of the grinding wheel (28) is effected.
 3. Thehand power tool of claim 1, wherein in at least one preselectable typeof motion, a self-rotation of the grinding wheel (28) is effected. 4.The hand power tool of claim 1, wherein in at least one preselectabletype of motion, an orbital motion of the grinding wheel (28) trips aself-rotation of the grinding wheel (28).
 5. The hand power tool ofclaim 1, wherein in at least one preselectable type of motion, anorbital motion of the grinding wheel (28) is effected, and the grindingwheel (28) is in a freewheeling mode with respect to a self-rotation. 6.The hand power tool of claim 1, wherein a rotation of at least one ofthe gear wheels (24, 38) can be prevented by means of the switch device(30).
 7. The hand power tool of claim 1, wherein the gear wheel (24)connected to the grinding wheel (28) has a set of external teeth,wherein the set of external teeth meshes with a set of internal teeth ofthe other gear wheel (38).
 8. The hand power tool of claim 7, whereinthe gear wheel (38) having the internal teeth is disposed in a slidebearing ring (36).
 9. The hand power tool of claim 1, wherein the atleast one locking bolt (64, 66) is guided in an axial, recess (52, 54)in the switching ring (46), wherein the recess if formed as an arc of acircle.
 10. The hand power tool of claim 9, wherein the switching ring(46), in the region of the axial recess (52, 54), has a chamfer (56, 58)formed as a ramp, wherein the at least one locking bolt (64, 66) isaxially shiftable by rotation of the switching ring (46) by means of thechamfer.
 11. The hand power tool of claim 1, wherein the grinding wheel(28) has an outline with at least one straight boundary edge and atleast one curved boundary edge.
 12. A hand power tool for grinding orpolishing, comprising a drive motor, a gear wheel coupled with drivemotor, and a grinding wheel (28) operatively connected to the gearwheel, wherein the gear wheel has a switch device (30), wherein at leasttwo types of grinding wheel motion can be preselectable by means of theswitch device, wherein the switch device includes a first locking boltfor engaging a recess of the first gear wheel to provide a firstgrinding wheel motion and a second locking bolt for engaging a recess ofa second gear wheel to provide a second grinding wheel motion.